9.B.265.  The Vitamin K Epoxide Reductase (VKER) Family 

The members of this family are between about 140 aas and about 600 aas in length. They have 4, 5 or 6 TMSs which for the small proteins encompase the whole protein, but for the larger proteins are always N-terminal.  They all show sequence similarity in their transmembrane domain, not in their C-terminal hydrophilic domains which are often very different in sequence.  Some have a C-terminal reductase domain and have been assigned to the bacterial VKER Family. Many clearly do not function in this capacity. There is no evidence that they function in transport.


TC#NameOrganismal TypeExample

Uncharacterized protein of 205 aas and 5 or 6 TMSs

UP of Candidatus Saccharibacteria bacterium


Vitamin K epoxide reductaseof 204 aas and 5 or 6 TMSs.

Reductase of Microbacterium hominis


Uncharacterized vitamin K epoxide reductaseof 170 aas and 4 TM

UP of Monashia flava


Uncharacterized protein of 143 aas and 4 TMSs.

UP of Anaerolinea thermolimosa


Uncharacterized dihydroorotate dehydrogenase (quinone) of 508 aas and 4 or 5 N-terminal TMSs that are sequence similar to the other members of this family.

UP of Candidatus Roizmanbacteria bacterium


Uncharacterized protein of 322 aas with an N-terminal 5 TMSs.

UP of Spirulina subsalsa


Uncharacterized protein of 394 aas with an N-terminal 5 TMS domain showing similarity to other members of this family.

UP of Candidatus Blackallbacteria bacterium